OPTICAL AND MAGNETOOPTIC PROPERTIES OF HGTE/CDTE SUPERLATTICES IN THE INVERTED-BAND SEMICONDUCTING REGIME

Low temperature infrared transmission and far-infrared magneto-optic transmission experiments were completed for a series of HgTe/CdTe superlattices (SLs). The SLs studied were grown with layer thicknesses intentionally chosen to make the samples inverted-band semimetals or inverted-band semiconductors, a new regime of the HgTe/CdTeSL which only recently has been predicted by theory. Cyclotron resonance of electrons in the first conduction subband H1 was observed in the far-infrared magneto-transmission experiments. From these measurements electron effective masses were calculated. The optical transition from the second heavy hole subband H2 to the second conduction subband E2 was observed in the infrared transmission experiments. The H2-E2 transition energy was observed to decrease with increasing SL well width L(z). In addition, the electron effective mass was found to increase as L(z) increases. Both of these observations indicate that all of the SL samples are, indeed, inverted-band SLs. This in turn implies that the valence band offset between HgTe and CdTe must be large, approximately 400 meV at 4.5 K.